If you click to join a Zoom meeting that you scheduled, but haven't signed into Zoom yet then you won't have your full host rights. You may want to record your meeting or do other advanced features, but can't select those items. This means you will need to "claim the host role".
1. Click on "Participants" at the bottom of your Zoom window
2. Click "Claim Host" in the lower right of the participants panel
3. When you see this pop-up window below it will ask for the "Host Key", but what you want to do is simply "Login to Claim Host"
4. Enter your email address and password for your account and you will have host rights to your meeting.